Rather than replacing university education, the trend of online learning has made classroom teaching more effective by getting professors to think more deeply about how they present information, said NUS lecturers involved in putting their modules online.

"There is no 'real' audience who can give immediate feedback. So you have to anticipate the response of the students," said Associate Professor Chung Keng Yeow of the department of physics.

Filming lecture video snippets that are only 10 to 12 minutes long also means that lecturers have to be very clear and focused in their delivery.

That requires a lot more planning, such as including examples of common errors made by students, said Ms Susan Tan, deputy director of the Centre for English Language Communication.

And lecturers have to pay much more attention to details. Said Ms Tan: "There is no eye contact with students... so you have to make sure there is always a smile in your voice."